Labels or badges can be used to display additional information, count, etc., small count, and label component.


.badge 

<span class="badge badge-light">4</span>


<button type="button" class="btn btn-primary">
  Notifications <span class="badge badge-light">4</span>
</button>

badges modifier classes to change the appearance of a badge.


<span class="badge badge-primary">Primary</span>
<span class="badge badge-secondary">Secondary</span>
<span class="badge badge-success">Success</span>
<span class="badge badge-danger">Danger</span>
<span class="badge badge-warning">Warning</span>
<span class="badge badge-info">Info</span>
<span class="badge badge-light">Light</span>
<span class="badge badge-dark">Dark</span>